As shown in FIG. 1, a conventional spring contact includes an upper contact pin 2, a lower contact pin 4 and a spring 3, in which the upper and lower contact pins are produced using a plate-shaped material. The spring contact is an important element of an IC test socket, in which the spring contact functions to electrically connect a lead of the IC to a PCB.
Hereinbelow, the construction, operational function and problems of the conventional spring contact will be described in detail with reference to FIGS. 2 through 6b. 
As shown in FIGS. 2 and 3, the conventional spring contacts are important elements of a socket 14, in which the spring contacts are installed in a nonconductive plastic molded socket body in such a way that the spring contacts have predetermined intervals, locations and heights, and come into contact with leads 12 of a semiconductor IC 11 that is a material subjected to a test, thereby performing the function of testing the IC.
The conventional spring contact includes: an upper contact pin which is provided with a contact portion that has a predetermined shape, two spring holding protrusions that are provided in left and right sides of the contact pin and limit the length of an assembled spring and prevent the assembled spring from becoming displaced, a spring holding surface that is formed by the two spring holding protrusions, and a body; a lower contact pin that is coupled to the upper contact pin in such a way that the upper and lower contact pins cross each other at right angles; and a spring 3 that is fitted over an assembly of the upper and lower contact pins 2 and 4 at a position between the upper and lower contact pins. Here, the body has two symmetric elastic portions, each of which has an oblique surface, a contact surface and a locking protrusion on an end thereof. A moving slit is formed between the two elastic portions and forms a moving space in which the lower contact pin can move, with a stop surface formed on an end of the moving slit, so that the moving slit movably receives the locking protrusions of the lower contact pin. The body further has a moving opening, which makes electric contact with the contact surfaces of the locking protrusions of the lower contact pin. Here, one end of the moving opening forms a stop bridge and the other end extends to the spring holding surface which is formed by the two left and right spring holding protrusions that function to limit the length of the assembled spring and to prevent the spring from undesirably becoming displaced.
The conventional spring contact is configured in such a way that the body of each of the upper and lower contact pins has a constant thickness within the range of up to the two elastic portions. Here, the thickness of the body within the range of up to the upper contact portion is typically determined to be about ⅓ of the width of the body and this is because a characteristic of the conventional spring contact is that the width of each of the two elastic portions and the width of the moving opening are determined to be almost equal to the thickness thereof.
A first problem that is experienced in the structure of the contact pins of the conventional spring contact, in which the thickness of each contact pin is determined to be about ⅓ of the width of the contact pin, resides in that a protruding part of the spring contact which protrudes from the molded socket body as shown in FIGS. 2 and 3 may be easily broken, as illustrated in FIG. 4.
A second problem of the conventional spring contact is caused by the structure of the contact pins and lies in that when the leads of an IC deviate from the contact portions of the contacts by about 0.15 mm during a practical IC test performed with a 0.5 mm pitch IC and a 0.5 mm pitch socket, in which the diameter of IC balls that function as the leads of the IC is 0.3 mm and the width and thickness of the contact portions of the contacts are 0.26 mm and 0.08 mm, respectively, the contact portions of the contacts do not deviate from the balls in a width direction of the contact pins of the conventional spring contacts; however, the contact portions of the contacts deviate from the balls in the thickness direction of the contact pins, as shown in FIGS. 6a and 6b. In the above state, the contact pins may break the IC balls or the contact portions may be form a bad contact with the balls, thereby causing bad test results.